A neuromodulation technique, known as optogenetics, involves directing light onto particular neurons in the brain. For instance, directing blue light onto particular neurons that are expressed channelrhodopsin-2 (ChR2) in the brain can stimulate neuronal activity. In some applications, the light can be used to control behavior in a subject. For experiments with freely behaving subjects, there are relatively few existing ways to deliver light to the subject. For instance, light may be delivered by an optical fiber, but the behavior of the subject may be influenced by the tether of the fiber. As another example, a head-mounted single light emitting diode (LED) system may be awkward, and may have relatively poor spatial resolution for light delivery inside the brain.